BANGKOK, Jan 5 (Reuters) - Thailand's headline consumer price index (CPI) dropped 0.83% in December from a year earlier, versus a 0.44% year-on-year drop in the previous month, the commerce ministry said on Friday.

The figure compared with a fall of 0.30% in December forecast in a Reuters poll. The core CPI was up 0.58% year-on-year in December, versus a forecast rise of 0.60%. (Reporting by Kitiphong Thaichareon, Satawasin Staporncharnchai and Chayut Setboonsarng)